Overview: How a solar hot water system works

If you've ever left a garden hose
lying across your lawn on a
sunny day and felt the nice hot
water coming out the end, you know that
sunlight is an effective water heater. Solar
hot water systems of yesteryear were often
leaky, failure-prone and ineffective, but the
industry has matured. Today, you can
choose between super-efficient, professionally
installed collectors and this less
expensive DIY-friendly system. And if
federal tax credits are available or additional state and
local incentives, you may be able to recoup
your investment in a few years, and enjoy
cheaper hot water for years beyond that.

Using a solar water system doesn't
mean surrendering the convenience of
your regular hot water system. Solar hot
water systems are designed to tie in to
conventional electric and gas water
heaters. The tank stores the solar-heated
water and serves as a backup heat source.
Even if the water from the collector isn't
shower-hot, you'll still save money since
your tank will have had a head start
heating the water. With all solar water
systems, it's vital that the panels be
installed where they will receive the most
direct sunlight. Ideally, you'll want to use a
south-facing section of roof. An east- or a
west-facing roof will also work, but you'll
need additional panels to collect the same
amount of heat.

Closed-Loop Solar Heating System

Here's how it works. When the controller senses that
the sun is shining and your tank
needs a warm-up, it signals the
pump to send water through the
black collector panels. The heated
water then flows into the storage
tank before it's channeled into the
heat exchanger. There, it transfers
its solar heat to the cooler water
coming from your hot water tank.
In this closed-loop system, the water
in the panel never mixes with
the water in the tank, so there's no
chance of contamination. When
the sun is down or the temperature
drops, the controller protects
the panel from freezing damage by
automatically draining the rooftop
panels into the storage tank.

A dependable, affordable DIY system

Joining roof sections

Flexible PEX tubing

The FAFCO kit's plastic PEX
water lines are simple to cut
(the tool is included) and
flexible, making them easy
to feed down to the utility
room.

Leakproof system

Flashing panels complete with rubber
grommets make for leakproof roof
penetrations. The hold-down straps
keep the panels in place.

Until now, most solar hot water systems
have required professional installation
with a price tag of $4,000 to $8,000.

But here is an affordable (about $2,000)
alternative that you can install in a weekend
if you have rudimentary plumbing
skills. FAFCO's Hot2O system (search fafco online) uses
unglazed polymer collectors (photo
above) instead of glazed flat-plates.
Although the system is less efficient than
professionally installed systems, the lightweight
panels don't require roof reinforcement
and are easy to install.

The kit includes everything you need to
connect the solar panels to your existing
electric water heater on a single-story
house (you may need extra tubing for
two-story homes). If you have a gas water
heater, you'll need to add a second tank to
store the solar-heated water and purchase
a hook-up kit from FAFCO. Or you can
use your old water heater as the storage
tank and replace it with a new, more efficient
water heater. The solar-heated water
from the second tank is connected to your
water heater, saving you energy and
money.

Estimate the Payback

To estimate the cost,
system size and payback
of a solar hot water system
for your home, go to the
American Solar Energy
Society's Web site, ases.org,
and click on “Go Solar.”
This site can also help you
locate a professional
installer for higher-efficiency
systems to help determine
the actual costs.